Long-Term Report:
Hot Chillys Bio-Silver Bi-Ply Outdoor Baselayer Top

All testing was done in Colorado, Utah, Arizona, and New Mexico. The terrains were forest, alpine tundra, canyon country, and badlands. Elevations ranged from 4000 ft/1220 m in Utah to 13,700 ft/4175 m in Colorado. Temperatures ranged from 10-85 F (-12 to 29 C). Weather conditions included intense sun, rain, snow, and wind.

How the Hot Chillys Shirt Was Worn
The Bio-Silver top was worn both as a base layer and as a hiking shirt for approximately equal times. As a base layer, the shirt was worn against my skin and various insulating layers were worn over it. As a hiking shirt, the Bio-Silver top was the only layer worn. On 10 occasions, totaling 49 days, the top was worn for an extended time without taking it off to test its anti-odor feature. The activities and time periods are summarized in the following table: 

Washing and Maintenance—The top was laundered after each trip or after 3-4 days of use. The washing instructions are: “Wash separately before wearing. Machine wash warm with like colors. Tumble dry low. Do not bleach. Do not iron.” I followed these directions, except a few times I hand washed it so I could use it again the next day. It was always hung to dry rather than putting it in the dryer (our preference). As reported in my Field Test Report, the only problem I had with the shirt was pilling. To determine how serious the pilling is, we de-pilled the right arm of the shirt on day 41 of the test after 14 days of use and de-pilled the entire right side of the shirt on day 92 of the test after 48 days of use.

My Experiences With the Hot Chillys Bio-Silver Shirt
Bio-Silver Top Compared to Hot Chillys Original Top—The Original Hot Chillys top is more stretchy and snug fitting.  The Bio-Silver top has a softer hand, is less stretchy, and has a relaxed but trim fit. Both tops are quite suitable for wear as a baselayer.

Casual Wear—When new, the Bio-Silver top was attractive to wear in casual social settings. After 11 days of outdoor use, the top was no longer suitable for social wear because of pilling.

Fit and Articulation—Size large fits me quite well. Note that my torso length (20.5 in/52 cm) and arm length (34 in/86 cm) are a bit on the long side compared to a “normal” size large. The sleeves cover my wrists, but I would prefer for them to be 1 in/3 cm longer. The body extends 5.5 in (14 cm) below my waist, which is about right. The shoulder seam is right on. Articulation is very good. When I extend my arms above my head, the sleeves pull down about 2 in (5 cm) below my wrists, but the body does not pull out of my pants at all. When I cross my arms, the sleeves pull up my arms about 1 in (3 cm) and the material tightens across the shoulders, but there is very little binding. The material is sufficiently stretchy to accommodate these movements, except for the sleeve pull.

Comfort—The Bio-Silver top is very comfortable to wear, even for extended periods. It has a soft hand and relaxed trim fit. The zip-neck can be zipped all the way up without rubbing or scratching the chin. I did not like the plastic red chili zipper pull, which dangled under my neck, so I removed it.

Anti-microbial Function—Ok, here are my results on the anti-stink factor! I wore the Bio-Silver top for 10 extended periods (ranging from 3 to 8 days, see table above) without taking it off. At the end of each extended wearing, my wife and I did a sniff test. We found that the top did have some detectable body odor, but it was not offensive. We rate the odor at a 3 on a scale of 10; 10 being the foul odor that a polypropylene top would take on during the same wear time. While I was wearing the top for these extended periods, I was not aware of any odor (in the top that is), and it remained quite comfortable to wear. The Bio-Silver technology really works!

Washing—My wife washed the top approximately 20 times during the 3-month test period. She machine-washed it with normal detergent, then hung it to dry. Obviously, the top got pretty dirty on several occasions. However, it laundered quite well considering that its color is white. There are some persistent stains where my pack (shoulder straps, hip belt, and backpad) contacted the shirt. Washing completely removed body odor.

Pilling—The top has a tendency to pill. This is the only negative that I have to report on the Bio-Silver top. The pilling started right away during the first 3 days I wore the top doing yard work, and continues to increase. The entire garment is pilled, but the pilling is concentrated on the seam side of the arms from the elbows to the wrists, and on the body where the arms rub against it. I would rate the pilling as a 7 on a scale of 10, 10 being badly pilled. The pilling is a significant factor that degrades the top’s appearance. After we de-pilled one arm of the shirt after 14 days of use, the pilling returned, but not to the level of the other arm that was not de-pilled. After we de-pilled one entire side of the shirt after 48 days of use, the pilling returned again, but not to the level of the other side that had not been de-pilled at all. Note that most of the pilling occurred because I often wore the top as a single layer (i.e., as a hiking shirt). If it had been worn exclusively as a baselayer, there would probably be much less pilling.

Warmth—The Bio-Silver top has a “Hot Chillys Warmth Factor” of 8 on a scale of 10. This rating system is handy for comparing one Hot Chillys top to another, and gives a general indication of how insulating it is and how it might be used. The level of warmth provided by the top met my expectations. Warmth is a very relative factor. It depends on exertion level, ambient temperature, color, radiant heat from the sun, and wind. For me, I found that the top worn as a single layer is comfortable down to 50 F (10 C) with no exertion, down to 40 F (4.4 C) with low exertion, down to 35 F (1.7 C) with moderate exertion, and down to about 25 F (-3.9 C) with high exertion. Under cloudy and/or windy conditions, these temperatures should be raised 10 degrees F (5.6 degrees C). At higher temperatures I wore the top comfortably from 55 to 85 F (12.8 to 29 C), depending on activity level. This fairly broad comfort range was in part due to its white color and front zipper.
 
Breathability—Because of its fabric weight, I would rate the Bio-Silver top as moderately breathable, about a 7 on a scale of 10; 10 being maximum breathability. Its 2-ply polyester fabric and finely ribbed construction certainly help with breathability, but it does not have the breathability of a thin highly textured polyester top. At cooler temperatures and low to moderate exertion, I found that the top effectively wicked away moisture and remained dry. Under high exertion hiking at 55 F (12.8 C) or higher, I found that the top would absorb sweat to the point of being wet, especially on my back when I was wearing a pack. Opening the front zipper helped a lot to increase ventilation and release moisture for increased comfort. When I stopped or reduced my exertion level, the top took 10-45 min (depending on temperature and how it was worn) to dry out under our typical low humidity conditions.

Wind Resistance—Owing to its breathability, the top has low wind resistance. At cooler temperatures, a stiff breeze around 10 mph (16 kph) is enough to feel chilled. However, the top works very well under a highly breathable wind shell.

Single Layer Performance—I wore the Bio-Silver top as a single layer, i.e., as a hiking top, about half the time. Note that it was my decision to wear it as a hiking top, and that Hot Chillys does not necessarily promote it for that type of use. As a hiking top, it performed very well and easily met my expectations. For comparison, I would say that its performance as a hiking shirt is equivalent to a mid-weight Patagonia Capeline zip-neck top, which I own. The material is equally durable. The fit of both garments is excellent. The Bio-Silver top has much less odor after extended wear. However, the Bio-Silver top pills while the Capeline top does not.

Baselayer Performance—The Bio-Silver top is an excellent baselayer, and that apparently is its intended use since the packaging calls it a baselayer. Used as a baselayer under other clothing in cold weather, the Bio-Silver top is very comfortable and transmits moisture very well under low or moderate exertion. An especially good combination was to wear the Bio-Silver top as a baselayer under a highly breathable EPIC softshell while hiking or snowshoeing at moderate or high exertion under cooler conditions (20-40 F/-6.7-4.4 C). In the 10 extended wear tests, I found it very convenient and effective to wear the Bio-Silver top as a hiking shirt during the day and as a baselayer the rest of the time. The top never came off; I simply layered clothing over it as needed. There was no problem with wearing it continuously for a week or more.

Durability—Except for pilling, the top is holding up very well. There is no unraveling of seams, stretching of cuffs, snagging, etc.
 
Tester Information
Tester Name: Will Rietveld
E-mail: willi_wabbit@bresnan.net
Gender: M
Age: 61
Height: 6' (183 cm)
Weight: 170 lbs (77.3 kg)
Torso Length: 20.5 in (52 cm)
Shirt Size: Large (16 in/41 cm neck, 34 in/86 cm sleeve length)
Location: Durango, Colorado, USA
Backpacking Background: 46 years of hiking and backpacking in the mountains and deserts of southwest Colorado, southeast Utah, New Mexico, and Arizona. I have also made numerous trips in Wyoming, Montana, Minnesota, Wisconsin, and upper Michigan. I have been a lightweight backpacker for many years, and an ultralight backpacker for 5 years. I have been retired for 6 years and backpack frequently. My wife and I present workshops on ultralight backpacking in our local area and have developed a website called Southwest Ultralight Backpacking. 

Acknowledgements
I would like to thank Hot Chillys and the BackpackGearTest group for selecting me to participate in this test.

Will Rietveld